#include <bits/stdc++.h>
using namespace std;
int n, m, hi, hj;
int mp[100][100];
long long dp[100][100];  
int di[8] = {-2, -1, 1, 2, 2, 1, -1, -2};
int dj[8] = {1, 2, 2, 1, -1, -2, -2, -1};

int main() {
  cin >> n >> m;
  cin >> hi >> hj;
  n += 4;
  m += 4;
  hi += 4;
  hj += 4;
  mp[hi][hj] = -1;
  for (int k = 0; k < 8; k++) {
    int ni = hi + di[k];
    int nj = hj + dj[k];
    mp[ni][nj] = -1;
  }
  dp[4][4] = 1;
  for (int i = 4; i <= n; i++) {
    for (int j = 4; j <= m; j++) {
      if (i == 4 && j == 4)  //要留意！！
        continue;
      if (mp[i][j] == -1)
        dp[i][j] = 0;
      else {
        dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
      }
    }
  }

  // 打印一下数组
  /*
  for (int i = 4; i <= n; i++) {
    for (int j = 4; j <= m; j++) {
      cout << dp[i][j];
    }
    cout << endl;
  }
  */

  cout << dp[n][m];
  return 0;
}